# Math Help - Log/Ex Equation

1. ## Log/Ex Equation

I cannot figure out this equation, solving for x.

4^2x - 4^x - 20 = 0

Can someone help?

Thanks,
Stefan

2. Originally Posted by millerst
I cannot figure out this equation, solving for x.

4^2x - 4^x - 20 = 0

Can someone help?

Thanks,
Stefan
note that this is $(4^x)^2 - (4^x) - 20 = 0$

let $4^x = y$, then you have

$y^2 - y - 20 = 0$

this is just a quadratic equation, hopefully you can solve it for $y$. when done, replace $y$ with $4^x$ and solve for $x$ by using the logarihm to the base 4

3. Thanks, helped a lot.